1. Technical Field
The present invention relates in general to improvements in disk drive systems and in particular to head gimbal assemblies for mounting read/write heads to an actuator hub, and to swage attachments for attaching head gimbal assemblies to actuator hubs.
2. Description of the Related Art
It has been a continuing objective of the disk drive industry to produce disk drive systems of increasing storage capacity, decreased size (or "form factor" as often used in the industry), and faster response time. One approach to increasing the storage capacity of a disk drive is to increase the number of disks. However, as the number of disks increases, the height of the disk drive also increases. To maintain the desired form factor of the disk drive, workers in the art are continually trying to reduce the spacing between disks. However, the space between disks must be sufficient to accommodate two read/write heads and two load beam assemblies on which the read/write heads are mounted.
While trying to reduce the spacing between disks, workers in the art are also trying to reduce the mass of the actuator and head gimbal assembly so as to decrease the response time of the disk drive. One way of reducing the mass of the head gimbal assembly is to bring the actuator hub closer to the center of the disk stack. This results in shorter, and thus lighter, head gimbal assemblies, and also in a disk drive having a smaller foot print.
One way to achieve the smallest possible spacing between the actuator hub and the center of the disk stack is for the actuator arms to fit between the disks. Therefore, the space between disks must be sufficient to accommodate not only two read/write heads and two load beam assemblies on which the read/write heads are mounted, but also an actuator arm and the attachment means for attaching the head gimbal assembly to the arm.
FIG. 7 shows one type of prior art head gimbal assembly attached to an actuator hub. As is shown in FIG. 7, each load beam 130 is connected to an actuator arm 124 by a mounting member 128. Therefore, each actuator arm 124, except for the upper and lower ones, has two load beams 130 attached to it by means of two mounting members 128. This means that between two disks 142 are located two load beams 130, one actuator arm 124, and two mounting members 128. Having two mounting members 128, one on each side of arm 124 adds considerably to the spacing required between disks.
Other prior art disk drives attempt to reduce the number of components between disks by attaching the load beams directly to the actuator arms, as, for example, by welding the load beams directly to the actuator arms. However, with the spacing between disks, and hence the spacing between actuator arms getting smaller and smaller, it is becoming harder and harder to weld, or otherwise attach, the load beams directly to the actuator arms.
Certain prior art disk drives attempt to reduce the number of components between disks by attaching the load beams to the same side of the actuator arm, requiring only one attachment means and thus less vertical room. However, this configuration is inadequate because the fixed ends of the two load beams are in contact with each other and thus allow undesirable vibrations to pass from one load beam to the other load beam.
Some prior art head gimbal assemblies, as explained above, are attached to actuator arms by attaching the load beams directly to the actuator arms. A different type of prior art head gimbal assemblies use a mounting plate onto which the load beams are mounted. The load beams are mounted to the mounting plate before the mounting plate is attached to the actuator arm. This makes attaching the load beams to the mounting plate easier since more room is available to make the attachment. Once the load beam assemblies are mounted onto the mounting plate, then the mounting plate is attached to the actuator arm.
One method of attaching the head gimbal assemblies to the actuator arms is by means of swaging techniques. Prior art swaging techniques involved swaging a spud, or boss, made of a hard material into an actuator arm made of a soft material. During prior art swage processes, a hard ball enlarges the spud cylinder, thus forcing the outside surface of the spud cylinder into the inside surface of the actuator arm hole, causing the outside surface of the spud cylinder to "bite" into the inside surface of the actuator arm hole. However, with the spacing between disks getting progressively smaller, the actuator arms must be made thinner and thinner. In order for the actuator arms to have sufficient rigidity and strength they sometimes need to be constructed of harder materials. Although swage connections are well known in the art, if a hard material is used for both the spud and the actuator arm, the current swaging techniques will not work adequately since the hard spud will not easily "bite" into the hard actuator arm hole.